The present invention relates to sealing nuts, and more particularly to a novel sealing nut having a nut body and sealing insert which provide improved performance and cost reduction over prior sealing nuts.
Sealing nuts are known which employ a nut body having a recess adjacent one end in which a sealing insert is retained, and wherein an internally threaded bore through the nut body and insert enable mounting of the sealing nut on a threaded shaft. In one prior sealing nut, such as disclosed in U.S. Pat. No. 4,019,550 which is owned by the assignee of the present invention and incorporated herein by reference, a coined annular lip on the nut body retains the sealing insert within the nut body recess. As the nut is threaded onto a threaded shaft, the annular lip is caused to engage a bearing surface through which the threaded shaft extends so that a protrusion or crown of the insert is compressed into sealing relation with the threaded shaft. Such sealing nuts find particular application as high pressure hydraulic sealing nuts but may also be utilized with equal efficiency in other applications. Other prior sealing nuts are described in U.S. Pat. No. 4,019,550 and their shortcomings discussed.
The various features enumerated for the sealing nut disclosed in U.S. Pat. No. 4,019,550 apply equally to the sealing nut of the present invention. In this respect, the sealing nut of the present invention provides metal-to-metal contact of the nut body against the bearing surface through which the threaded shaft extends so that the sealing insert flows into sealing engagement with the threaded shaft; both the nut body and sealing insert are tapped with a continuous axial thread; the sealing nut is reusable without significant loss of sealing ability; and the nut can withstand high pressures without leakage. In addition, the sealing nut of the present invention lends itself to significantly reduced manufacturing costs. For example, most prior sealing nuts employ relatively expensive manufacturing techniques wherein the nut body is made by cold forming. A shortcoming of this technique is that close dimensional tolerances are difficult to achieve. Also, the prior sealing inserts have been made by injection molding techniques requiring movement of die members in both horizontal (X) and vertical (Y) axes during the injection process, thus requiring more costly dies with resulting increased manufacturing costs.
One of the primary objects of the present invention is to provide a novel improved sealing nut which includes a nut body having an annular sealing insert retained within a recess adjacent one end of the nut body, the nut body and sealing insert enabling reduced manufacturing costs while facilitating high pressure sealing of a threaded shaft extending from a bearing surface against which the sealing nut is engaged.
A more particular object of the present invention is to provide a novel sealing nut having a nut body which receives an annular sealing insert, and wherein the insert is bidirectionally insertable into a recess in the nut body and retained therein by an annular collar formed over the insert in a manner to dynamically preload the sealing insert with resulting greater fluid tight sealing about a threaded shaft on which the nut is mounted.
In carrying out the present invention, a metallic nut body is formed with a polygonal first end defining external wrench flats and having an axial bore, and an annular wall or collar adjacent an opposite end which defines an internal generally cylindrical recess concentric with the axial bore. A generally donut shaped insert made of a high impact resilient resin material is inserted into the recess. The annular wall or collar of the nut body is formed, as by coining, over the insert in a manner to mechanically encapsulate and dynamically preload the insert such that the insert undergoes a cross-sectional twisting action or partial inversion which causes the outer end of a cylindrical axial bore in the insert to increase slightly in diameter, and the diameter of the inner end of the insert bore to decrease. A uniform thread bore is formed axially through the nut body and sealing insert to facilitate mounting onto a threaded shaft. In installing the sealing nut, the nut body is torqued against a bearing surface through which the threaded shaft projects so that the coined annular wall or collar engages the bearing surface and the sealing insert is further dynamically compressed into fluid tight relation with the threaded shaft.
A feature of the sealing nut in accordance with the invention lies in the utilization of an annular nylon sealing insert which is generally symmetrical about a median plane transverse to the axis of the insert. This enables the insert to be bidirectionally inserted into the recess in the nut body. The insert undergoes a cross-sectional twisting action or partial inversion as the annular wall or collar of the nut body is formed over and compressed against the insert. This causes an outwardly facing end of the insert to be stretched outwardly and the inwardly facing end of the insert to be compressed inwardly adjacent an axial bore through the annular insert. This action dynamically preloads the insert and causes it to fill any voids in the nut body recess. An internal thread is then formed in the axial bore of the nut body and sealing insert.
Typical sealing nuts of the type employing sealing inserts encapsulated within a nut body require that the sealing insert engage at least a three-pitch length of the threaded shaft on which the nut is installed. A significant advantage of the sealing nut in accordance with the present invention is that for most applications the sealing insert forms a very effective liquid tight seal while engaging approximately a single-pitch length of the threaded shaft, thus requiring a significantly reduced volume of sealing insert material over prior sealing nuts.
Another feature of the sealing nut in accordance with the invention lies in pre-loading the sealing insert by forming the annular wall or collar of the nut body over the insert so as to compress the insert and stretch its outer exposed surface in a manner to inhibit shear and abrasion of the insert as it engages the runout area of a tapped bore in a bearing surface from which a threaded shaft extends during installation of the nut onto and removal from the threaded shaft.
Further objects, features and advantages of the sealing nut of the present invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawing wherein like reference numbers designate like elements throughout the several views.